Rotary fluid seal

ABSTRACT

A rotary fluid seal comprising a housing having a fluid pressure chamber therein, with a shaft mounted for rotation in the housing and having a longitudinal passageway therein for communicating with the fluid pressure chamber within the housing. The housing is provided with port means extending therethrough communicating with the fluid pressure chamber for introducing a fluid therein. Sealing means are positioned within the housing and cooperate with the fluid pressure chamber therein for controlling the flow of fluid from within the fluid pressure chamber into the longitudinal passageway of the shaft without escapement from around the shaft. The sealing means comprises a rotatable member of rigid construction, concentrically carried by, and rotatable with the shaft and having an axial face serving to define a wall portion of the fluid pressure chamber, and a seal member carried by the housing and having a flexible annular lip portion sealingly engaging the axial face of the rotatable member concentrically therewith, and also serving to define a wall portion of the fluid pressure chamber.

United States Patent n91 Sigmon [451 Jan. 29, 1974 ROTARY FLUID SEAL[75] Inventor: James W. Sigmon, Charlotte, NC.

[73] Assignee: Sigmon Corporation, Charlotte,

221 Filed: Sept. 18,1972

21 Appl. No.: 289,798

Primary ExaminerWilliam T. Dixson, Jr. Assistant Examiner-Robert 1.Smith Attorney, Agent, or Firm-Daniel E. McConnell [57] ABSTRACT Arotary fluid seal comprising a housing having a fluid pressure chambertherein, with a shaft mounted for rotation in the housing and having alongitudinal passageway therein for communicating with the fluidpressure chamber within the housing. The housing is provided with portmeans extending therethrough communicating with the fluid pressurechamber for introducing a fluid therein. Sealing means are positionedwithin the housing and cooperate with the fluid pressure chamber thereinfor controlling the flow of fluid from within the fluid pressure chamberinto the longitudinal passageway of the shaft without escapement fromaround the shaft. The sealing means comprises a rotatable memberiofrigid construction, concentrically carried by, and rotatable with theshaft and having an axial face serving to define a wall portion of thefluid pressure chamber, and a seal member carried by the housing andhaving a flexible annular lip portion sealingly engaging the axial faceof the rotatable member concentrically therewith, and also serving todefine a wall portion of the fluid pressure chamber.

11 Claims, 6 Drawing Figures ROTARY FLUID SEAL This invention relates toa rotary fluid seal adapted particularly for introducing a pressurizedfluid, such as compressed air, into a rotatable shaft while preventingleakage of the fluid thus being introduced. Heretofore various types ofrotary fluid joints have been devised to accomplish essentially the samepurpose. However, in an effort to provide a leakproof seal whentransmitting fluids under pressure, it has usually been necessary toutilize seals having engaged surfaces held in engaging position by aspring or the like, with the seals having a relatively large surfacearea of contact. This normally results in the generation of asubstantial amount of friction between sealing members, which, becausethe friction is distributed over a relatively large surface area, isrelatively inefficient, but nevertheless has a tendency to increase theenergy needed to maintain the desired speed of shaft rotation, and torequire frequent replacement or repair of the sealing members.

It is therefore an object of this invention to provide a rotary fluidseal which utilizes the pressure of the fluid passing therethrough toengage sealing means for thus preventing leakage.

It is another object of this invention to provide a sealing means of theaforementioned type, which compensates for gradual wear to lengthen thefrequency of replacement and to provide a continuously leakproof seal.

Some of the objects of the invention having been stated, other objectswill be evident as the description proceeds, when taken in connectionwith the accompanying drawings, in which FIG. 1 is a perspective viewofa rotary fluid seal according to a preferred embodiment of theinvention;

FIG. 2 is a vertical cross section taken substantially along line 22 ofFIG. 1;

FIG. 3 is an exploded, perspective view thereof;

FIG. 4 is a perspective view of a rotary fluid seal according to anotherembodiment of the invention, shown connected to a rotating drum, with aportion of the rotating drum broken away;

FIG. 5 is a vertical cross-sectional view taken substantially along line55 of FIG. 4; and

FIG. 6 is a partially exploded perspective view of the rotary fluid sealof FIG. 4.

Referring now more specifically to the drawings, a rotary fluid sealaccording to a preferred embodiment thereof is shown in FIG. 1 andcomprises a housing, broadly indicated by reference numeral 10, andhaving a shaft 11 mounted therein for rotational movement. While thestructure is herein referred to by the term rotary fluid seal, the termjoint is used altematively. The housing, according to FIGS. 2 and 3,comprises an intermediate cylindrical housing member 12 having anaxially extending bore 13 therethrough, central portions of which definea fluid pressure chamber 13a, as will be described in detailhereinafter. Enclosing the opposing ends of the housing member 12 arecylindrical end caps 14, 15, which are releasably secured in anysuitable way to the opposing axial ends of the housing member 12, as forinstance, by threaded bolts 16 extending through holes 17 around theperiphery of the axial face of the end caps 14, 15, and positioned inthreaded bores 18 in the respective axial faces of the housing member12. The end caps 14, have aligned, substantially concentric holes 20,21, respectively, ex-

tending axially therethrough for accommodating the rotatably mountedshaft 11.

Formed on the inner surface of the housing member 12 are axially opposedannular recessed portions 23, 24, as is best shown in FIG. 3. A raisedportion of the inner surface of housing member 12 intermediate therespective opposed recesses 23, 24, defines an annular, integrallyformed rib 25, the purpose of which will be described in detailhereinafter.

A fluid is introduced into the fluid pressure chamber 13a by port means,broadly indicated by reference numeral 26 and comprising radial bore 27extending through the body and rib 25 of housing member 12 andcommunicating with the fluid pressure chamber 13a, with a hose 28 havinga threaded coupling 280, connected to the housing member 12 incommunication iwth the bore 27.

A cylindrical hub 41 the purpose of which will be set forth hereinafter,is suitably positioned, as by a press fit, on the shaft 11 for'rotationtherewith, and in substantial radial alignment with the integrallyformed annular rib 25 of housing member 12.

Extending longitudinally through the rotatably mounted shaft 11 is apassageway 29, which communicates with the fluid pressure chamber 1311through at least one laterally or radially extending passageway 30 inthe shaft 11 and hub 41.

Positioned in spaced relation to each other on the shaft 11 within thehousing 10 and serving to prevent the escape of fluid therefrom aresealing means, broadly indicated by reference numeral 40 and comprisingan opposed pair of rotatable members 42, 43, in the form of annulardisks, and a pair of annular seal members 50, 51. The annular disks 42,43 are positioned concentrically on the shaft 11 and connected, as bythreaded bolts 45, to opposing axial faces 41a, 41b of the hub 41, andare preferably formed of a noncorrosive metal such as stainless steel.To prevent leak age of fluid from the fluid pressure chamber 13a to theshaft 11 at the area of connection of the hub 41 and the annular disks42, 43, box ring seals 48 are provided, positioned in annular recesses49 in the opposing axial faces 41a, 41b, of the hub 41, and concentrictherewith.

Disks 42, 43 have convex, inwardly opposed axial faces 42a, 43a,respectively, and outwardly opposed, concentric annular neck portions42b, 43b, respectively. The neck portions 42b, 43b extend outwardly fromthe housing member 12 through holes 20, 21 of end caps 14, 15,respectively. The axial faces 42a, 43a of annular disks 42, 43,respectively, as shown in FIG. 2, are positioned on the shaft 11 insubstantial radial alignment with recessed portions 23, 24,respectively, of housing member 12.

Forming a seal with the convex axial faces 42a, 43a, of the annulardisks 42, 43, respectively, are the annular seal members 50, 51,supportingly carried in the annular recessed portions 23, 24,respectively, of housing member 12 of housing 10. The annular sealmembers 50, 51, are shown in the form of a ring made of a suitableresilient or elastomeric material, such as molded tetrafluoroethylene(TFE) fluorocarbon resin. Integrally formed on the annular rings 50, 51,are somewhat curved, radially inwardly extending, flexible tapered lipportions 50a, 51a, respectively, having a very thin free end. Whenpositioned in respective recessed portions 23, 24, as shown in FIG. 2,the very thin, free end of the tapered lip portions 50a, 51a, ispositioned in substantially hairline engagement with the respectiveconvex axial faces 42a, 43a, of the annular disks 42, 43.

From the foregoing description, and as best illustrated in FIG. 2, itwill be apparent that the walls of fluid pressure chamber 13a aredefined by the opposing radial surfaces of the annular rib 25 of housingmember 12 and hub 41, in conjunction with portions of the convex axialfaces 42a, 43a, of annular disks 42, 43 and the lip portions 50a, 51a,of annular rings 50, 51.

Shaft 11, with sealing means 40 positioned thereon, can be mounted forrotation in the housing by any suitable means. One such suitable meansis illustrated in FIG. 2, and comprises a pair of anti-friction members,shown as annular ball bearing assemblies 54, 55, positioned around shaft11 in an annular recess provided on the inner axial face of cylindricalend caps 14, 15, respectively. When positioned in these recesses, theinner radial surfaces of the ball bearing assemblies 54, 55 ride inengagement with reduced outer end portions of the outwardly extendingneck portions 42b, 43b of the annular disks 42, 43.

Serving to prevent axial dislocation of the sealing means 40 within thehousing 10, or more specifically, to maintain the proper relativelocation of annular disks 42, 43, with the annular rings 50, 51,respectively, are annular collets 57, 58, each having agradual externalaxial taper. The end of collets 57, 58 having the smaller externaldiameter is positioned on the shaft 11 outside the housing 10 andadjacent cylindrical end caps l4, 15, respectively. Then they are wedgedaxially inwardly a distance determined by the taper of collets 57,-58,into a clearance 59 between the outer end of neck portions 42b, 43b ofannular disks 42, 43, respectively, and the radial surface of shaft 11.

The collets 57, 58 are held in their wedged position by a pair ofannular compression nuts 60, 61, having internally threaded portionswhich engage matingly threaded portions located on the outer end of neckportions 42b, 43b, respectively.

In operation, as is evident from the foregoing description, a fluid isintroduced into said pressurized fluid chamber 13a through the radialbore 27. The fluid then enters the longitudinally extending passageway29in shaft 11 through the laterally extending passageway 30. The pressurein fluid pressure chamber 13a caused by the presence of the pressurizedfluid therein acts on lip portions 50a, 51a, as is shown by arrows inFIG. 2, so that they are maintained in sealing engagement with theconvex axial faces 42a, 43a of annular disks 42, 43, respectively. Itwill be understood that the lip portions 50a, 51a are in engagement withthe convex axial faces 42a, 43a at all times, but that the pressureexerted on the flexible annular lip portions 50a, 51a increases thefriction therebetween, and creates a tighter seal.

As is evident, the higher the pressure within the fluid pressure chamber13a, the tighter the seal that will be provided thereby, provided thepressure is within the normal operating limits of the rotary fluid jointas a unit. It will also be understood that in normal operation, shaft 11is intended to rotate, but that the rotary fluid joint will operatecontinuously to provide a proper seal even though the shaft 11 isrotated intermittently, or not at all. Furthermore, it is apparent thatthe flexible annular lip portions 50a, 51a, will gradually wear away,and as this occurs, the pressure in fluid pressure chamber 13a willcontinue to maintain the lip portions 50a, 51a in sealing engagementwith the convex axial faces 42a, 430 by urging the lip portions 500,51a, gradually outward along the curved surface of the convex axialfaces 42a, 43a.

From the foregoing description, it is seen that hub 41 and the annulardisks 42, 43, together with collets 57, 58 and compression nuts 60, 61are all carried on and rotate with shaft 11, while annular rings 50, 51remain relatively stationary, being supported, as describedhereinbefore, by the walls of housing 12 defining recesses 23, 24,respectively.

A rotary fluid seal according to a modified form of the invention, andintended particularly for introducing a pressurized fluid, such ascompressed air, into the axial end of a rotating shaft connected to adrum D, for example, is shown in FIGS. 4 through 6. The rotary fluidseal comprises a housing, broadly indicated by reference numeral 70, andas is best shown in FIGS. 5 and 6, housing comprises a first cylindricalhousing member 71, having an axially extending predetermined largediameter bore 72 therein communicatively connected with an axiallyextending concentric smaller bore 72a. Interconnected with the firsthousing member 71 is a second cylindrical housing member 73, having anoutside diameter corresponding to the outside diameter of the firsthousing member 71, and having a relatively small diameter concentricbore 74 therein. When housing member 71, 73 are suitably interconnected,as by a plurality of threaded bolts 79 in matingly threaded, alignedbores positioned around the outer adjoining axial peripheries of thefirst and second housing members, the interior walls of the housingmembers 71, 73, define axially extending concentric boresthe smalldiameter bore 74 in housing 73 communicating with the large diameterbore 72 in the first housing member 71 which in turn communicates withbore 72a which serves to define a portion of a fluid pressure chamber.

Positioned within the large bore 72 and small bore 74 is alongitudinally extending shaft, broadly indicated by reference numeral76, and having a longitudinally extending passageway 77 thereincommunicating with the bore 72a through the axial face of the portion ofshaft 76 positioned in large bore 72. It will be noted that the diameterof shaft 76 positioned in small bore 74 is substantially smaller thanthe diameter of the small bore 74 so as to accommodate antifrictionmeans as will be described in detail hereinafter.

A threaded portion 76a of the shaft 76 extends outwardly from the smalldiameter bore 74 in the second housing member 73 for interconnectingwith a rotating structure, such as the drum D in FIGS. 4 and 5. Aplurality of flat portions 76b are provided on the radial surface of theshaft 76 to provide a gripping surface for a wrench or the like, tofacilitate easy loosening and tightening of shaft 76 in the Drum D.

Carried on the end of shaft 76 within the large diameter bore 72 is anannular disk 78, preferably integrally formed therewith, and preferablyformed of a longwearing, non-corrosive material such as stainless steel,and having a convex axial face 78a communicating with the fluid pressurechamber bore 720. Also positioned in large diameter bore 72 andsupported by the inner walls of the first and second cylindrical housingmembers 71, 73 is a resilient annular ring 80, similar to rings 50 and51 previously described, having a radially extending, tapered flexibleannular lip portion 80a. Lip

portion 80a curves into engagement with axial face 78a of annular disk78 to form a relatively thin, hairline seal therewith. As is best shownin FIG. 5, a fluid pressure chamber 85 is formed substantially by thefluid pressure chamber bore 72a, with the free end of lip portion 800,central portions of axial face 78a, and adjacent wall portions of largediameter bore 72, together forming an axial wall of the fluid pressurechamber 85.

Serving to introduce a fluid into fluid pressure chamber 85 are suitableport means, comprising an axial bore 86 extending concentrically throughthe axial face of first housing member 71, and communicating with fluidpressure chamber 85 therein. A hose 87, having a threaded coupling 87a,is connected to the first housing member 71 by means of a matinglythreaded portion 871) on the inner walls thereof defining bore 86.

Shaft 76 is mounted for rotational movement within the second housingmember 73 by means of a pair of antifriction means comprising spacedapart annular ball bearing assemblies 89, 90, positioned snugly aroundshaft 76 in a reduced radial portion thereof. The inner walls of smalldiameter bore 74 engage the outer radial surfaces of annular ballbearing assemblies 89, 90 with the annular ball bearing assemblies 89,90 being maintained in axial, spaced apart relation by an annularspacing ring 91 positioned therebetween.

In operation, as is evident by the foregoing description, a pressurizedfluid is introduced into fluid pressure chamber 85 through hose 87. Asillustrated in FIG. 5, bore 86 is substantially concentric with and inclose opposition to passageway 77 in shaft 76 so that a substantialamount of the fluid is passed almost directly thereinto. However,pressurized fluid fills fluid pressure chamber 85 and, as shown byarrows in FIG. 5, forces the lip portion 80a of annular ring 80 into theproper sealing engagement with axial face 78a of annular disk 78. Itwill be understood, as earlier noted in the first embodiment of theinvention, that lip portion 80a is intended to always be in engagementwith axial face 78a, the fluid pressure increasing the frictional forcesbetween the two members for effecting a tighter seal. It will be furtherunderstood, as also mentioned earlier, that as annular disk 78 rotateswith shaft 76, the engaged surface of lip portion 80a will graduallywear away, so that as lip portion 80a becomes shorter, the pressure influid pressure chamber 75 will tend to urge it outwardly along axialface 78a, thus compensating for wear.

It will be apparent that this embodiment is, as is the first embodiment,constructed so that the greater the pressure of the fluid flowtherethrough, the better the seal obtained, due to the increased forcesurging the lip portion 80a into sealing engagement with the axial face78a of annular disk 78.

It will thus be seen that there is described herein two embodiments of arotating fluid seal, each having relatively few parts, but providing asubstantially leakproof seal, the quality of which is relativelyunaffected by a predetermined degree of wear of the lip portions of theannular rings provided in each embodiment.

It will be understood that various details of the invention may bechanged without departing from the scope of the invention. Furthermore,the foregoing description is for purposes of illustration only and notfor purposes of limitation the invention being defined by the claims.

That which is claimed is:

l. A rotary fluid seal comprising a housing having a fluid pressurechamber therein, a shafted mounted for rotation in said housing andhaving a longitudinal passageway therein communicating with said fluidpressure chamber within the housing, said housing having port meansextending therethrough communicating with said fluid pressure chamberfor introducing a fluid therein, and sealing means positioned withinsaid housing and cooperating with said fluid pressure chamber thereinfor controlling the flow of fluid from within the fluid pressure chamberinto the passageway of said shaft without escapement from around theshaft, said sealing means comprising a rotatable member of rigidconstruction, concentrically carried by, and rotatable with said shaftand having an axial face serving to define a wall portion of said fluidpressure chamber, and a seal member carried by said housing and having aflexible annular lip portion sealingly engaging said axial face of saidrotatable member concentrically therewith and also serving to define awall portion of said fluid pressure chamber.

2. A rotary fluid seal according to claim 1, wherein said rotatablemember on said shaft comprises an annular disk with said axial facethereof being of convex configuration for compensating for wear of saidflexible annular lip portion of said seal member and for effecting aseal under variable pressure conditions.

3. A rotary fluid seal according to claim 1, wherein said flexibleannular lip portion of said seal member extends substantially radiallyinwardly into engagement with said axial face and wherein said lip istapered to provide a very thin free end for effecting substantiallyhairline engagement with said axial face.

4. A rotary fluid seal according to claim 1, wherein said seal membercomprises an elastomeric annular ring.

5. A rotary fluid seal comprising a housing having a fluid pressurechamber therein, a shaft mounted for rotation in said housing and havinga longitudinal passageway therein communicating with said fluid pressurechamber within the housing, said housing having port means extendingtherethrough communicating with said fluid pressure chamber forintroducing a fluid therein, and sealing means positioned within saidhousing and cooperating with said fluid pressure chamber therein forcontrolling the flow of a fluid from within the fluid pressure chamberinto the passageway of said shaft without escapement from around theshaft, said sealing means comprising a rotatable annular disk of rigidconstruction, concentrically carried by said shaft and having an axialface serving to define a wall portion of said fluid pressure chamber,and an annular ring, carried by said housing and having a flexibleannular lip portion concentrically engaging said axial face 'of saidrotatable annular disk and also serving to define a wall portion of saidfluid pressure chamber.

6. A rotary fluid seal comprising a housing having a fluid pressurechamber therein, a shaft mounted for rotation in said housing and havinga longitudinal passageway therein communicating with said fluid pressurechamber within the housing, said housing having port means extendingtherethrough communicating with said fluid pressure chamber forintroducing a fluid therein, and sealing means positioned in saidhousing and cooperating with said fluid pressure chamber therein forcontrolling the flow of fluid from within the fluid pressure chamberinto the passageway of said shaft without escapement from around theshaft, said sealing means comprising a spaced pair of opposed, rotatablemembers of rigid construction, concentrically carried by, and rotatablewith said shaft,'each of said rotatable members having an axial faceserving to define a wall portion of said fluid chamber, and a pair ofspaced seal members carried by said housing with each having a flexibleannular lip portion concentrically engaging the respective axial face ofsaid pair of rotatable members and also serving to define a wall portionof said fluid pressure chamber.

7. A rotary fluid seal according to claim 6, including a hub membermounted on said shaft between said pair of opposed rotatable members androtatable therewith, and said shaft and said hub member having acommunicating laterally extending passageway therethrough communicatingwith said longitudinally extending passageway in the shaft and with saidfluid pressure chamber.

8. A rotary fluid seal according to claim 7, wherein seals arepositioned between opposing endsof said hub member and said rotatablemembers for preventing leakage of fluid therebetween.

9. A rotary fluid seal comprising a housing having a fluid pressurechamber therein, a shaft mounted for rotation in said housing with anend portion thereof terminating within the housing, said shaft having alongitudinal passageway therethrough communicating with said fluidpressure chamber, said housing having port means extending therethroughcommunicating with said fluid pressure chamber for introducing a fluidtherein, and sealing means positioned within said housing andcooperating with said fluid pressure chamber therein for controlling theflow of fluid from within the pressure chamber into the passageway ofsaid shaft without escapement from around the shaft, said sealing meanscomprising a rotatable member of rigid construction, concentricallycarried adjacent said end portion of, and rotatable with, said shaft andhaving an axial face serving to define a wall portion of said fluidpressure chamber, and a seal member carried by said housing and having aflexible annular lip portion sealingly engaging said axial face of saidrotatable member concentrically therewith, and also serving to define awall portion of said fluid pressure chamber.

10. A rotary fluid seal according to claim 9, wherein said rotatablemember is integrally formed on said shaft.

11. A rotary fluid seal according to claim 9, wherein said port meanscommunicating with said fluid pressure chamber comprises a boreextending through said housing in opposition to and closely adjacentsaid longitudinal passageway in said shaft for passing a pressurizedfluid from said bore into the longitudinal passageway of said shaft.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 788,653 Dated January 29, 1974 Inventor(s) In W i on It is certified thaterror appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

Column 2, line 17, correct the spelling of "with" Column 3, line 2,following 'hair1ine" insert "sealing-- Column 6, line 2, delete"shafted" and insert therefor --shaft- Signed and. sealed this 1st dayof October 1974.

(SEAL) Attest:

McCOY M. GIBSON JR. C. MARSHALL DANN Commissioner of Pa tents AttestingOfficer USCOMM-DC 60376-969 i ".l. COVIIIIIINT nnmuc omcl nu o-au-auFORM PC4050 (10-69)

1. A rotary fluid seal comprising a housing having a fluid pressure chamber therein, a shafted mounted for rotation in said housing and having a longitudinal passageway therein communicating with said fluid pressure chamber within the housing, said housing having port means extending therethrough communicating with said fluid pressure chamber for introducing a fluid therein, and sealing means positioned within said housing and cooperating with said fluid pressure chamber therEin for controlling the flow of fluid from within the fluid pressure chamber into the passageway of said shaft without escapement from around the shaft, said sealing means comprising a rotatable member of rigid construction, concentrically carried by, and rotatable with said shaft and having an axial face serving to define a wall portion of said fluid pressure chamber, and a seal member carried by said housing and having a flexible annular lip portion sealingly engaging said axial face of said rotatable member concentrically therewith and also serving to define a wall portion of said fluid pressure chamber.
 2. A rotary fluid seal according to claim 1, wherein said rotatable member on said shaft comprises an annular disk with said axial face thereof being of convex configuration for compensating for wear of said flexible annular lip portion of said seal member and for effecting a seal under variable pressure conditions.
 3. A rotary fluid seal according to claim 1, wherein said flexible annular lip portion of said seal member extends substantially radially inwardly into engagement with said axial face and wherein said lip is tapered to provide a very thin free end for effecting substantially hairline engagement with said axial face.
 4. A rotary fluid seal according to claim 1, wherein said seal member comprises an elastomeric annular ring.
 5. A rotary fluid seal comprising a housing having a fluid pressure chamber therein, a shaft mounted for rotation in said housing and having a longitudinal passageway therein communicating with said fluid pressure chamber within the housing, said housing having port means extending therethrough communicating with said fluid pressure chamber for introducing a fluid therein, and sealing means positioned within said housing and cooperating with said fluid pressure chamber therein for controlling the flow of a fluid from within the fluid pressure chamber into the passageway of said shaft without escapement from around the shaft, said sealing means comprising a rotatable annular disk of rigid construction, concentrically carried by said shaft and having an axial face serving to define a wall portion of said fluid pressure chamber, and an annular ring, carried by said housing and having a flexible annular lip portion concentrically engaging said axial face of said rotatable annular disk and also serving to define a wall portion of said fluid pressure chamber.
 6. A rotary fluid seal comprising a housing having a fluid pressure chamber therein, a shaft mounted for rotation in said housing and having a longitudinal passageway therein communicating with said fluid pressure chamber within the housing, said housing having port means extending therethrough communicating with said fluid pressure chamber for introducing a fluid therein, and sealing means positioned in said housing and cooperating with said fluid pressure chamber therein for controlling the flow of fluid from within the fluid pressure chamber into the passageway of said shaft without escapement from around the shaft, said sealing means comprising a spaced pair of opposed, rotatable members of rigid construction, concentrically carried by, and rotatable with said shaft, each of said rotatable members having an axial face serving to define a wall portion of said fluid chamber, and a pair of spaced seal members carried by said housing with each having a flexible annular lip portion concentrically engaging the respective axial face of said pair of rotatable members and also serving to define a wall portion of said fluid pressure chamber.
 7. A rotary fluid seal according to claim 6, including a hub member mounted on said shaft between said pair of opposed rotatable members and rotatable therewith, and said shaft and said hub member having a communicating laterally extending passageway therethrough communicating with said longitudinally extending passageway in the shaft and with said fluid pressure chamber.
 8. A rotary fluid seal according to claim 7, wherein seals are positioned between opposing ends of said hub member and said rotatable members for preventing leakage of fluid therebetween.
 9. A rotary fluid seal comprising a housing having a fluid pressure chamber therein, a shaft mounted for rotation in said housing with an end portion thereof terminating within the housing, said shaft having a longitudinal passageway therethrough communicating with said fluid pressure chamber, said housing having port means extending therethrough communicating with said fluid pressure chamber for introducing a fluid therein, and sealing means positioned within said housing and cooperating with said fluid pressure chamber therein for controlling the flow of fluid from within the pressure chamber into the passageway of said shaft without escapement from around the shaft, said sealing means comprising a rotatable member of rigid construction, concentrically carried adjacent said end portion of, and rotatable with, said shaft and having an axial face serving to define a wall portion of said fluid pressure chamber, and a seal member carried by said housing and having a flexible annular lip portion sealingly engaging said axial face of said rotatable member concentrically therewith, and also serving to define a wall portion of said fluid pressure chamber.
 10. A rotary fluid seal according to claim 9, wherein said rotatable member is integrally formed on said shaft.
 11. A rotary fluid seal according to claim 9, wherein said port means communicating with said fluid pressure chamber comprises a bore extending through said housing in opposition to and closely adjacent said longitudinal passageway in said shaft for passing a pressurized fluid from said bore into the longitudinal passageway of said shaft. 